1. Field of the Invention
The present invention relates to a substrate surface deflecting device for use in an apparatus such as an exposure apparatus suitable for exposing a printed circuit board, a plate of a liquid crystal display element, and the like to irradiation such as light for producing thereon patterns with a large area.
2. Statement of the Related Art
As disclosed in Japanese Patent Unexamined Publication Nos. 56-130738 (U.S. Pat. No. 4,391,511), 58-67026 (U.S. Pat. No. 4,504,045), 57-204547 (U.S. Pat. No. 4,475,223), and 61-239638 (U.S. Pat. No. 4,666,291), conventional exposure apparatuses employ piezoelectric elements as vertical displacement driving sources. The arrangement of these exposure apparatuses is such that a chuck and the piezoelectric elements are not fixed to each other but held in contact with each other, a chamber below the chuck is evacuated, and the chuck is thereby pulled downwardly to be pressed against the piezoelectric elements, such that the surface of the substrate can be deformed or deflected by the piezoelectric elements.
An improvement of this method is disclosed in Japanese Patent Unexamined Publication No. 61-102735, in which the chuck of the substrate is moved vertically up and down by piezoelectric elements, but the lower side of the chuck is not held under vacuum, and the chuck and the piezoelectric elements are connected to each other by resilient supports.
In the above-described prior art, since the possible magnitude of displacement or stroke by the piezoelectric elements is small, this method is inadequate in deflecting substrates, such as printed circuit boards, which have a large warping or deflection. In addition, since a method of assembly is complicated, a large number of assembly processes are required. Furthermore, in the apparatus in which the chuck is pulled dowardly under vacuum, it is necessary to provide a substantially vacuum chamber on the lower side of the chuck. Therefore, there has been drawbacks in that a sealing mechanism becomes complicated, and that the overall size of the apparatus becomes large.